unit imglib;

interface
uses  Windows, sysutils, Graphics, ImgList,  Vcl.Controls, System.Types;

function DisabledImages(AImageList: TCustomImageList): TImageList;

implementation

function DisabledImages(AImageList: TCustomImageList): TImageList;
const
  MaskColor = 5757;
var
  ImgList: TImageList;
  ABitmap: TBitmap;
  i: Integer;

  function ConvertColor(AColor: TColor): TColor;
  var
    PixelColor, NewColor: Integer;
  begin
    PixelColor := ColorToRGB(AColor);
    NewColor   := Round((((PixelColor shr 16) + ((PixelColor shr 8) and $00FF) +
      (PixelColor and $0000FF)) div 3)) div 2 + 96;
    Result     := RGB(NewColor, NewColor, NewColor);
  end;

  procedure ConvertColors(ABitmap: TBitmap);
  var
    x, y: Integer;
  begin
    for x := 0 to ABitmap.Width - 1 do
      for y := 0 to ABitmap.Height - 1 do
      begin
        ABitmap.Canvas.Pixels[x, y] :=
          ConvertColor(ABitmap.Canvas.Pixels[x, y]);
      end;
  end;

begin
  ABitmap := TBitmap.Create;

  try
    ImgList := TImageList.Create(nil);
    ImgList.Width := AImageList.Width;
    ImgList.Height := AImageList.Height;
    ImgList.Clear;
    for i := 0 to AImageList.Count - 1 do
    begin
      ABitmap.Canvas.Brush.Color := MaskColor;
      ABitmap.Canvas.FillRect(rect(0, 0, AImageList.Width, AImageList.Height));
      AImageList.GetBitmap(i, ABitmap);
      ConvertColors(ABitmap);
      ImgList.AddMasked(ABitmap, ConvertColor(MaskColor));
    end;
    Result := ImgList;
  finally
    ABitmap.Free;
  end;
end;

end.
